Formalisation of the tribo-oxidation mechanisms of a cobalt-based alloy subjected to fretting-wear : influence of the temperature

Dreano, A.

PhD Tesis (2019)

This manuscript presents a multi-physical analysis of the fretting wear damages observed on a cobalt-based alloy. It has been showed that the wear process is severe at low temperature whereas a mild wear process takes place at high temperature. At low temperature, the wear process is driven by a synergetic action of the oxidation of the surface and the abrasion of the newly formed oxide layer. An analytical formulation is then proposed by taking into account these two phenomena. However, the proposed wear law is only valid when the wear debris is immediately ejected out of the interface. Yet, when the temperature is high enough, the debris starts to agglomerate into the interface changing completely the tribological response. At high temperature, a protective tribolayer is formed by a compaction and sintering processes of the wear debris which drastically limits wear. The oxido-abrasive wear law, describing the wear behaviour at low temperature, is then modified in order to take into account the tribolayer formation. The tribolayer, also called “glaze layer”, has a multi-layerered structure whose formation is strongly linked to the oxidation and diffusive properties of the alloying elements. In the light of these results, the tribological mecanisms providing complete protection of the interface from further wear are discussed.